If you look at the ingredients for Alka-Seltzer, you will find that it contains citric acid and sodium bicarbonate (baking soda). When you drop the tablet in water, the acid and the baking soda react -- this produces the fizz.
Shake and Bake A new and increasingly widespread technique also known as one pot, this condenses the anhydrous method's many steps and requires only a plastic soda bottle, the size of which depends on the quantity of meth the cook intends to make.
From Top Secret Recipes www.topsecretrecipes.com. This recipe is practically identical to the one Kraft uses for their Shake'n Bake bread coating. The only difference you'll find is that the real Shake'n Bake contains beet powder - a hard to find ingredient that gives the mix a dark orange tint.